Multiprotocol Label Switching (MPLS) is a mechanism applied in networks that directs data from one network node or network element to the next based on locally significant short path labels rather than long, globally significant, network addresses, thereby avoiding complex lookups in a routing table. For example, MPLS is described, in part, in Request for Comments (RFC) 3032 “MPLS Label Stack Encoding,” January 2001, the contents of which are incorporated by reference herein. Fast Reroute (FRR) is an MPLS resiliency technique providing fast traffic recovery upon link or router failures for critical services. Upon any single link or node failures, the technique would be able to recover impacted traffic flows at the level of 50 ms. FRR is described in RFC 4090 “Fast Reroute Extensions to RSVP-TE for LSP Tunnels,” May 2005, the contents of which are incorporated by reference herein. Resource Reservation Protocol-Traffic Engineering (RSVP-TE) extensions are defined in RFC 3209 “Extensions to RSVP for LSP Tunnels,” December 2001, the contents of which are incorporated by reference herein.
RFC 3209 describes the use of RSVP, including all the necessary extensions, to establish Label Switched Path (LSP) in MPLS. Since the flow along an LSP is completely identified by the label applied at the ingress node of the path, these paths may be treated as tunnels. An application of LSP tunnels is traffic engineering with MPLS as specified in RFC 2702, “Requirements for Traffic Engineering Over MPLS,” September 1999, the contents of which are incorporated by reference herein.
RFC 4090 defines RSVP-TE extensions to establish backup LSP tunnels for local repair of LSP tunnels. These mechanisms enable the re-direction of traffic onto backup LSP tunnels in 10 s of milliseconds, in the event of a failure. Two approaches are defined, a one-to-one backup approach creates detour LSPs for each protected LSP at each potential point of local repair and a Facility Backup (FB) approach creates a bypass tunnel to protect a potential failure point. By taking advantage of MPLS label stacking, the bypass tunnel approach can protect a set of LSPs that have similar backup constraints. Both approaches can be used to protect links and nodes during a network failure. The described behavior and extensions to RSVP allow nodes to implement either approach or both and to interoperate in a mixed network.
In the FB approach, local protection is provided on a Point of Local Repair (PLR) by creating a backup path over another tunnel which originates on the PLR and terminates on a Merge Point (MP), bypassing the protected router. The FB approach requires an existing Facility Backup tunnel. Alternatively, such a Facility Backup tunnel can also be auto-created, in the absence of an “existing” Facility Backup Tunnel. Currently, there is no such mechanism to control the auto-generation on a per protected tunnel basis; it is something which must be configured on the PLR.